Isomerization of hydrocarbons



Artur orrics 2,271,043 ISOMERIZATION 0F HYDR-OCARBONS van Peski,Amsterdam, Netherlands, assignor' to Shell Development Company, SanFrancisco, Calif., a corporation Adrianus Johannes of Delaware NoDrawing. Application September 5, 1939, Se-

rial No. 293,427. ber 16, 1938 In the Netherlands Septem- 9Claims.-(Cl.260--676) The present invention relates to a process for thecatalytic ,isomerization. of hydrocarbons. More particularly, theinvention relates to the I catalytic conversion of normal butane andnormal pentane to isobutane and isopentane respectively.

Normal butane and normal pentane are obtained in a relatively pure statein large quantitiesfrom petroleum and natural gas. These hydrocarbonsare .chemically quite unreactive and have poor ignition characteristics.Isobutane and isopentane', on the other hand, are chemically much morereactive but occur naturally only to a very limited extent. They may bereadily alkyllated with olefines, for example, to produce saturatedhydrocarbons which are especially desired for premium and aviationgasoline, and they may be readily dehydrogenated to the respectivetertiary olefins-which, in turn, are excellent starting materials forthe syntheses of a wide variety of useful and valuable products. In viewof the abundance of normal butane and normal pentane and theever-increasing demand for isobutane and isopentane, acommerciallypractical process for the conversion of the normal isomersto the branched chain isomers is of great value.

An object of the invention is to provide a more practical and economicalprocess for the production of isobutane and/or isopentane by thecatalytic isomerization of normal butane and/or normal pentane. A moreparticular object is to provide a process whereby normal butane and/ ornormal pentane may be catalytically isomerized at a practical rate. witha minimum formation of undesirable products due to side reactions.Another object of the invention is to provide a process for thecatalytic isomerization of normal bu tane and/or normal pentane whereinthe active life of the catalyst is materially increased. 0th er objectsof the invention will be apparent in the following description of theprocess.

In its more general aspect, the process of the invention comprisesisomerizing the hydrocarbon or mixture of hydrocarbons to be treatedwith the aid of an acid-acting metal halide catalyst- These Thehydrocarbon treated need not necessarily be a pure individualhydrocarbon but may be a mixture of one or more hydrocarbons. Thus, theinvention provides a practical process for converting the normal butaneand normal pentane contents of commercial hydrocarbon mixtures, such asare obtained from natural gases, petroleum distillates, crackeddistillates, etc.',- to the more valuable branched chain isomers.Especially suitable mixtures of hydrocarbons are the so-calledbutane-butylene fractions and pentaneamylene fractions from which theunsaturated hydrocarbons have been substantially removed.

Treatment of such mixtures which contain a certain amount of normalbutane and/or normal pentane, results in very materially increasingtheir content of branched chain isomers and enhancing their value as rawmaterials for use in alkylation, production of tertiary olefins, etc.

) invention and their'content of branched chainisomersmateriallyincreased without loss due to decomposition and sidereactions and while realizing a maximum active life of the catalystemployed; Other mixturesof saturated hydrocarbons, such as cuts ofstraight run gaso1ine,.

casinghead gasoline, etc., containing appreciable quantities of normalbutane and/or normal pentane, may also be advantageously treated toproduce products which are more suitable for alkylation with olefins andhave superior ignition characteristics.

The hydrocarbon or mixture of hydrocarbons treated is preferablysubstantially free of materials which are polymerized by theisomerization catalyst under the reaction conditions. Ac cording to apreferred embodiment of the invention, any olefins, diolefins, or otherdetrimental impurities in the hydrocarbon or hydrocarbon mixture to betreated are removed prior to use by a suitable treatment, such as with amineral acid or with a portion of spent catalyst from the process.

The isomerization is preferably effected with the aid of an aluminumhalide such as aluminum chloride or aluminum bromide. Although 1 thealuminum halides are, in general, the most practical and efficientcatalysts, such other acidacting halide catalysts as exert a catalyticinfluence on the isomerization of hydrocarbons, e. g. the halides of Be,Zn, Zr, Nb, Ta, Sb, and B, may also, if desired, be employed.Exceptionally suitable catalyst combinations are mixtures of an aluminumhalide with a free metal of the group consisting of Al, Be, Mg, Zn, Cu,and Fe.

The catalysts are preferablyemployed in the solid state in any suitableform such as granules, powder, or pellets of the desired size,preferably deposited on or mixed with a suitable solid supportingmaterial. Particularly efiective catalysts are produced when aluminumchloride is supported in or intimately mixed with one of the varioussiliceous and/or aluminous materials of natural or synthetic originwhich contain an appreciable amount of firmly-bound water.. Suitablematerials of the category are, for example, the naturally-occurringminerals and clays, such as pipe clay, bauxite, fullers earth,bentonite, kaolin, Florida earth, meerschaum, infusorial earth,kieselguhr, diatomaceous earth, montmorillonite, the permutites, and thelike; the various treated clays and clay-like materials, such as Tonsil,Celite, Sil-O-Cel, Terrana and the like; and artificially preparedmaterials, such as Activated Alumina, silica gel, the artificialpermutites, and the like. The aluminum halide may, moreover, be simplysuspended in the liquid reaction mixture, or it may be employed in theform of a complex double compound such, for instance, as those known asGustavsons compounds (C 1903 II 1113) andthe Ansolvo Acids (Ann 455227-253).

The isomerization is executed, according to the process of the presentinvention, under a pressure of hydrogen. It is found that hydrogenexerts a remarkable and unexpected influence in the isomerizationreaction and that an appreciable pressure of hydrogen is, in general,very beneficial. By the use of suitable pressure of hydrogen, highertemperatures aifording more practical reaction rates may be employed,undesirable side'reactions are repressed, and the active life of thecatalyst is materially increased.

It is alsofound that moderate hydrogen pressures, i. e. from about oneto about five atmospheres (measured at 20 C.), tend to a certain extentto promote the isomerizing activity of the catalyst. Thus, whereasunpromoted aluminum Table I Per cent isoparaflin in the reaction productPartial ressure of Cl in atmospheres Since, however. the halogen halidespromote cracking and other undesirable side reactions, especially atelevated temperatures where practical rates of isomerization prevail, ithas hitherto been considered necessary to limit the amount of hydrogenhalide employed to about 0.2 to 2% and not more than 5% by weight of thehydrocarbon undergoing treatment, and the full benefit of thesepromoters has not been utilized.

An important feature of the present invention is that the beneficialeffect of much larger con- .centrations of hydrogen halides may beemployed while the side reactions, which usually accompany their use,are substantially obvihalides are known not to catalyze isomerization toany appreciable extent, it is found that, in the case of theisomerization of normal butane and normal pentane, the isomerization maybe effected even in the absence of'a hydrogen halide if a suitablepressure of hydrogen is applied.

This is illustrated by the following examples:

' EXAMPLE I 100 parts by weight of a commercial pentane fractioncontaining 85.9% normal pentane and 14.1% isopentane were charged, alongwith 10 parts of aluminum bromide .and sufiicient hydrogen'to create apartial pressure of five atmospheres (measured at 20 C.), into arotating autoclave. After heating the mixture for ten hours-at 80 C. theproduct was found to contain 31.7% normal pentane and 67.8% isopentane.

EXAMPLE II according to the present process, in the absence- 76 ated.This is illustrated in the following examples:

EXAMPLE III 80 parts of normal butane were treated with 40 parts ofaluminum chloride and 8 parts of hydrogen chloride for four hours at 120C. In the absence of hydrogen, '7 5% of the normal butane was isomerizedto isobutane while 89% of the normal butane was consumed by undesirableside reactions. Upon repeating the experiment using substantialpressuresof hydrogen, it was found that the conversion to isobutane increased andthe side reactions decreased. When employing a partial pressure ofhydrogen of only three atmospheres (measured at 20 C.), for example, theconversion to isobutane increased to about 50%, and theconsumptionofnormal butane by side reactions was aiready decreased toabout 9%.

EXAMPLE IV parts of normal pentane were treated with,

154 parts of normal pentane and 15.4 parts of technical aluminumchioride were introduced into an iron autoclave of suitable capacity,whereupon gaseous hydrogen chloride was pressed in until the partialpressure of the hytected.

' following table:

drogen chloride was 17 atmospheres at 20 C. Subsequently, hydrogenwaspressed in until its partial pressure wa 33 atmospheres at 20 C. Theautoclave was then heated and kept at 80 C. for 17 hours. After removalof aluminum chloride, hydrogen chloride and hydrogen, the productobtained consisted of 60.5% by weight of isopentane, 37.2% by weight ofnormal pentane and 2.3% by weight of products formed by sidereactions.Upon repeating the experiment in the absence of hydrogen but underotherwise identical conditions, the pentane was practically en-'- tirelyconsumed by undesirable side reactions and no appreciable quantity ofisopentane was de- EXAMPLE VI A series of experiments was made whereinthe aluminum chloride catalyst was generated in the reaction system byreaction between metallic aluminum and hydrogen chloride. In eachexperiment 80 parts of a butane fraction containing 4% isobutane wereheated to 120 C. for ten about 5% and an increase in efiiciency of aboutAs the hydrogen pressure is increased, this promoting action disappearsand further. increase of the hydrogen pressure gradually decreases theisomerizing activity of the catalyst until at very high hydrogenpressures the isomerization is entirely inhibited. Thus, for example, lnthe isomerization of pentane at a tem-= perature of 40. C. theisomerization was completely inhibited when a hydrogen pressure of 200atmospheres was employed.

Since the optimum pressure of hydrogen- (measured at C.) according tothe process of the invention depends upon the hydrocarbon or hydrocarbonmixture being treated, the temperature, the kind and amount of catalyst,the amount of hydrogen halide, and possibly also upon the type ofapparatus and the reaction time,

hours 'with metallic aluminum and hydrogen chloride and with or withoutadded hydrogen in.

a V2A steel rotating autoclave. The results-of the respectiveexperiments are tabulated in the Table II Reaction product Alt .H(2:ddfd P t par 5 par 5 a er can Per cent Per cent if 'gg isobutaneN-butane Although the process of the present invention is applicable andadvantageous when executed in the total absence of a hydrogen halide andalso in the presence of less than 5% by weight of a hydrogen halide, itis, in general, most advantageous when the partial pressure is greaterperatures higher than about'200 C. and temthan oneatmosphere andpreferably at least v three atmospheres (measured at 20 C.) The hydrogenhalide may be added directly in any convenient manner, as a liquid, gasor solution. Furthermore, the hydrogen halide may, if desired, begenerated in the reaction zone by introducing a material which willdecompose orreact under the prevailing conditions to form the desiredhydrogen halide, may be added for this purpose are, for example, water,organic hydroxy compounds, inorganic applicable hydrogen pressures mayvary from a fraction of an atmosphere up to several hundred atmospheres.In general, under the more usual conditions, excellent results may beobtained using hydrogen pressures in the range of from about 1 to aboutatmospheres and usually from about 2 to about 20 atmospheres.

An other and important advantage of the present process is that highertemperatures aifording more favorable isomerization rates may beemployed. By the use of suitable pressures of hydrogen, thedecomposition and other side peratures ranging fromabout 30 C. to about180 C. are usually most practical.

The process according to the present inven- .tion may be carried out inthe gaseous phase as Suitable materials which salts, such as PbSO4-2HC1,CuSO4-2HCl, containing molecular-bound hydrogen halide, alkyl halides,and the like.

This promoting action of hydrogen, when used under suitable pressures,is also noticed when the catalyst is promoted with a hydrogen halide.This is illustrated by the followingexample:

EXAMPLE VII 100 parts of normal pentane were reacted with 10 parts ofaluminum chloride and 10 parts of hydrogen chloride in a VzA steelrotating autoclave at--40 C. for five hours. The conversion toisopentane amounted to 32%. Upon repeating the above experiment underthree atmose pheres pressure of hydrogen (measured at 20 C.)

This represents an increase in conversion of the conversion toisopentane amounted to 37%.- H

well as in the liquid phase and either batchwise or continuously.

When the isomerization is carried out in the gaseous or vaporous phase,the presence of even .very small amounts of hydrogen, such as forexample 1% or even less, is mostly suflicient for. its exerting a verymarked favorable influence on the course of the-reaction. This isillus-' trated by the following examples.

Example VIII A mixture of about 85.6 mol. normal butane,

14 mol. isobutane. and 0.4% hydrogen was passed, in the presence of 6%by weight of dry HCl, over a catalystpreparedby converting into tabletsa mixture of 70 parts by weight technical AlCla and 30 parts by weightkaolin under an excess pressurev 'of- 15 atm. at a temperature .of

, C. The velocity with'which the gas mixture was passed over thecatalyst amounted to 0.8 kg. per litre catalyst per hour, whilst thepartial pressure of the HCl amounted to about 1.5

'atm.. and. that of the hydrogen to about 0.08

atm'. During the first 200 hours of continuous operation the isobutanecontent of the reaction product exceeded 40%.. Upon the operation be-'mg continued the average isobutane content slowly decreased and after500 hours it amounted whilst the total quantity of isobutane producedwas '75 kg. per litre of catalyst.

EXAMPLE IX v A gas mixture consisting of about mol. isobutane, about 89mol. normal butane and about 1 mol. hydrogen, which mixture had ,beenobtained byhydrogenation of a mixture of butanes and butenes, wasintroduced at the bottom of a reaction tower filled with a catalystconsisting of a mixture of 70% by weight technical aluminium chloride(with an iron content below 0.3% by weight) and 30% by weight kaolin(which had been dried to about 300 C.), which mixture had beencompressed to pills of about 5 mm. diameter. The throughput of the gasmixture amounted to 0.65 kg. per litre catalyst per hour. The gasmixture was previously dried by contacting it with silicagel or solidpotassium hydroxide and was freed of any further impurities by passingit over technical aluminium chloride and then over common salt at normaltemperature.

Together with the gas mixture about 8 mol. hydrogen chloride wasintroduced into the reaction tower. The temperature in the reactiontower amounted to 9095 C. and the pressure to about atm. v

At the bottom the tower was equipped with a device for collecting thesludge formed, thus making possible the continuous withdrawal thereof.

The reaction product leaving the tower at the top was first led into acooled space, in order to separate entrained aluminium chloride, in

which space a mechanical device was provided for returning the aluminiumchloride to the reaction tower. Subsequently a separation of thehydrogen was effected by further cooling, whilst in a followingfractionating apparatus the rehad been formed.

After 500 hours operation the activity of the catalyst had practicallynot decreased.

The several examples herein submitted to illusbutane with an aluminumhalide catalyst, the step of executing the isomerization reaction in thepresence of at least 1 atmosphere pressure of a hydrogen'halide promoteras measured at 20 C. and between 0.08 and 33 atmospheres pressure ofadded hydrogen, the partial pressure of said hydrogen being suflicientto substantially repress undesirable side reactions, but insuflicient tosubstantially repress the isomerization reac-- tion.

3. In a process for the isomerization of normal pentane with an aluminumhalide catalyst, the step of executing the isomerization reaction at atemperature below 200 C. in the presence of a hydrogen halide promoterand between 0.08 and the presence of a hydrogen halide promoter and,between 0.08 and 33 atmospheres pressure of added hydrogen; the partialpressure of said hydrogen being. sufficient to substantially repressundesirable side reactions, but insuflicient to substantially repressthe isomerization reaction.

5. In a process for the isomerization of normal pentane with an aluminumhalide catalyst, the step of executing the isomerization reaction underbetween 0.08 and 33 atmospheres pressure of hydrogen, the partialpressure of said hydrogen being sufiicient to substantially repressundesirable side reactions, but insuflicient to substantially repressthe isomerization reaction.

6. In a process for the isomerization of normal butane with an aluminumhalide catalyst, the step of executing the isomerization reaction underbetween 0.08 and 33 atmospheres pressure of hydrogen, the partialpressure of said hydrogen being 'sufiicientto substantially repressundesirable side reactions, but insufiicient to substantially repressthe isomerization reaction.

7. In a process for the isomerization of a saturated aliphatic.hydrocarbon containing more than 3 and less than 6 carbon atoms with analuminum halide catalyst, the step of executing the isomerizationreaction under between 0.08 and 33 atmospheres pressure of hydrogen, thepartial pressure of said hydrogen being suflicient to substantiallyrepress undesirable side reactions, but

trate various aspects of the invention are not to be considered aslimiting the invention. It is to be understood that modifications willbe readily apparent to those skilled in the art and that no limitationsare intended other than those imposed by the scope of the appendedclaims.

I claim as my invention:

1. In a process for the isomerization of normal pentane with an aluminumhalide catalyst, the step of executing the isomerization reaction at atemperature below 200 C. in the presence of insufficient tosubstantially repress the isomerization reaction.

8. In a process for the isomerization of normal pentane with an aluminumchloride catalyst, the step of executing the isomerization reaction at atemperature-below 200 C. in the presence of -a hydrogen chloridepromoter and between 0.08

and 33 atmospheres pressure of added hydrogen, the partial pressure ofsaid hydrogen being suflicient to substantially repress undesirable sidereactions, but insufilcient to substantially repress the isomerizationreaction.

9. In a process for the'isome'rization of normal butane with an aluminumchloride catalyst, the

at least 1 atmosphere .pressure of a hydrogen halide promoter asmeasured at 20 C. and bestep of executing the isomerization reaction inthe presence of a hydrogen chloride promoter and between 0.08 and 33atmospheres pressure of added hydrogen, the partial pressure of saidhydrogen being suflicient to substantially repress undesirable sidereactions, but insuflicient to substantially repress the isomerizationreaction.

ADRIANUS OHANNES VAN PESKI.

